Finest natural fibre for an animal

Endemic to the Tibetan Plateau, the chiru – or Tibetan "antelope" (Pantholops hodgsonii) – has the finest natural fibre, with soft undercoat hairs being as little as 7–10 micrometres in diameter. The trade in the chiru's sought-after wool – known locally as "shahtoosh" – has led to dramatic declines in their numbers, perhaps from as many as a million in the early 1900s to approximately 150,000 (as of 2009). The species is currently listed as Near Threatened by the IUCN.

The chiru hairs upon which this record is based were reported in a paper that appeared in the Textile Research Journal on 1 November 1999; they were dark brown in colour, but it was not stated where they were collected on the body.

The vicuña (Vicugna vicugna) of the South American Andes and the musk ox (Ovibos moschatus) from the Arctic both have very fine wool as well: 13.5 micrometres and 11–15, micrometres, respectively. By comparison, typical merino wool – the finest wool from domestic sheep – has a diameter of 15–27 micrometres.